The present invention relates to an MR (magnetic resonance) imaging method and an MRI (magnetic resonance imaging) coil, and more particularly to an MR imaging method and an MRI coil capable of improving an SNR (signal-to-noise ratio).
There has heretofore been proposed a technique of conducting parallel MRI with a plurality of coils having significantly different sensitivity distributions from one to another disposed in the phase encoding direction (for example, see Patent Document 1). The parallel MRI is a technique for producing an MR image by receiving signals from a subject by a plurality of coils and processing them in parallel for reducing the imaging time.
Moreover, the SNR in a SENSE (sensitivity encoding) technique is known to be inversely proportional to a g factor (geometry factor) (for example, see Non-patent Document 1). The SENSE technique, which is one type of parallel MRI, is a technique of decimating the phase encoding steps, instead of receiving signals by a plurality of coils in parallel, for reducing the imaging time. The “g factor” is a value determined by the position of coils and the SENSE algorithm.
[Patent Document 1] Japanese Patent Application Laid Open No. 2003-79595 ([0009]).
[Non-patent Document 1] “Getting a Good Command of MRI” (Japanese original title: “MRI Ouyou Jizai”), edited by Jun'ichi Hachiya and another, published by Medical Review Co., Ltd., (Nov. 10, 2001), pp. 9-10.
Such conventional parallel MRI and SENSE techniques employ a pair of single-turn coils (a single-turn coil is a coil whose number of turns is one) that are disposed to face each other across a space for accommodating a subject.
The single-turn coil, however, does not have high sensitivity in close proximity to its coil plane, and hence, the rate of change in sensitivity is not high in the face-to-face direction and the g factor is increased, leading to a problem that a sufficiently high SNR cannot be obtained.